A pointing device of a computer generates a signal to move a cursor that is displayed on a screen of the computer according to an operation of a user. As the pointing device, there is a pointing stick other than a mouse and a touch pad. The pointing stick is provided among keys of a keyboard. One such pointing stick is called a track Point®. The pointing stick has been mainly used in a laptop personal computer (laptop PC) for the reasons that operation can be performed while a finger is placed in a home position, an operation space is not required as a case of using a mouse, and operation is easily performed while a computer is supported on knees in a train or a vehicle.
Since the pointing stick includes a circuit substrate or a shield cover, the pointing stick has influence on the entire thickness of a laptop PC. In order to reduce the thickness of a laptop PC, it is demanded to facilitate further thickness and size reduction of the pointing stick. FIGS. 6A and 6B are views illustrating a structure of a pointing stick in the related art. FIG. 6A is a perspective view of a pointing stick 10, and FIG. 6B is a cross-sectional view illustrating a state in which the pointing stick is attached to a keyboard assembly.
An operation post 11 is covered by a cap of which a surface is formed of a soft material such as silicon rubber (not illustrated) and is used to move a cursor by applying force in a horizontal direction by a finger of a user. The operation post 11 is arranged almost in the center of the keyboard assembly so as to easily move the cursor while the user operates keys. The operation post 11 is bonded to a sensor printed circuit board (PCB) 13 with an adhesive. Strain gauges (not illustrated) are bonded on the rear surface of the sensor PCB 13 in X and Y directions.
The sensor PCB 13 is bonded to a base PCB 15 with an adhesive. A circular opening is formed in the center portion of the base PCB 15, and the sensor PCB 13 causes a tensile force or compression force to be applied to the strain gauge with the force applied to the operation post 11. The base PCB 15 has a terminal unit 21 connected to a logic PCB 17 by soldering. The base PCB 15 is bonded to a base plate 19 with an adhesive. The logic PCB 17 has an operational amplifier, a processor and the like mounted thereon and converts a change in the electrical resistance of the strain gauge into voltage, and further, generates a digital signal corresponding to a moving direction, a moving amount, and a moving speed of the cursor according to the force applied to the operation post 11.
The logic PCB 17 outputs the generated digital signal to a controller of a motherboard through flexible flat cables (FFCs) 27 which are connected to the terminal unit 23. A metal shield cover 25 covers the entire pointing stick 10 to suppress influence of electromagnetic waves emitted from the motherboard handling a high frequency signal. The base plate 19 is attached to the shield cover by a screw. The pointing stick 10 is provided with a waterproof sheet 53 and a waterproof ring 55 for waterproofing countermeasures and attached to a keyboard substrate 51 using a screw hole of the base plate 19.